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Unit 18: Biology Part 1 Page 32 of 60
contains cavities filled with air. around you, in order to avoid
These cavities connect to the predators.
respiratory system of birds, and Eggs are usually
give them an even lighter weight found in nests.
body for flight. Most bird nests
Birds also have wings, which make are very
flight possible. The wing is elaborate,
important for both lift and thrust. although some
In other words, the wing helps the birds, such as
bird get off the ground (lift) and the albatross,
move forward (thrust.) If you simply lay their
think about different type of wings, eggs in a scrape
you can see that birds use their in the ground and others, including
wings differently. the common guillemot, do not lay
A larger eggs in nests at all.
wing, About 100 species, including the
like that cuckoos, are brood parasites.
of an These birds lay their eggs in the
eagle or nests of other birds, referred to as
hawk, the host. When the parasite bird
can be is born, the host parent will care
spread for it, even though it may hurt
out. This provides enough lift to their own offspring. Some
allow the bird to soar without using parasites even have shorter
much energy. On the other hand, incubation times that hosts, so that
the small wing of a sparrow or blue the parasite will hatch first, destroy
jay will need to be flapped more to the eggs of the host, and ensure
create the thrust needed to keep that it gets the most resources
the bird off the ground. Although from the host parent.
this is an effective way of flying, it The process of building a nest is
requires more energy than soaring. not something birds need to be
You certainly already know that taught. Nest building is an innate
birds lay eggs. Bird eggs are often behavior, or instinct, which means
a certain color so they will blend in that the animal, (in this case a
with their surroundings. This is an bird) was born knowing how to do
example of camouflage, or it. Certain actions involved in
looking like some non-living thing caring for the nest are also innate.
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